An Advanced Placement class at Richard Montgomery High School in Rockville, Md. (Mark Gail/The Washington Post)

The writer is a senior fellow at the Ethics and Public Policy Center.

The College Board set off a firestorm last year by issuing what many saw as a left-biased curriculum framework for its Advanced Placement U.S. History course. This summer’s much-discussed revisions to that framework amount to less than meets the eye. The underlying bias remains, and few of the vaunted changes will filter down to the classroom.

The controversy, moreover, points to what will likely be our next great education debate. The College Board’s determination to issue detailed curriculum frameworks for all of its AP exams, in combination with the expansion of the AP program over the past decade or so, has brought the United States to the threshold of something nobody claims to want: a national curriculum.

Emerging around the time of the 1957 Sputnik launch, the early AP program highlighted the national interest in cultivating the very best students. In the 1980s and ’90s, worries about failing schools and an interest in maximizing opportunity for all spread AP courses from a few elite institutions to schools across the country. Initially, the focus was rightly on finding and educating talented students, regardless of income, ethnicity or race. Gradually, however, AP came to be seen as a method for quickly overcoming the achievement gap between poor and minority students and others, regardless of preparation.

In the 2000s, politicians of both parties jumped onto this expansion bandwagon. Federal and state governments began subsidizing AP testing fees. Several states mandated AP courses in all schools. Meanwhile, the Clinton, Bush and Obama administrations moved aggressively to expand AP participation.

As a result, the proportion of public high school graduates who took at least one AP exam rose from 18.9 percent in 2003 to 33.2 percent in 2013. The College Board has argued that all students who score a certain minimum on the PSAT would benefit from AP classes, regardless of preparation and eventual performance on the test. By College Board reckoning, 42.6 percent of 2013 graduates ought to have taken at least one AP class. A few schools have even begun to automatically enroll most students in AP courses. There, as in Lake Wobegon, all children are above average.

A substantial body of scholarly literature now raises questions about the excesses of AP expansion. Yale University’s William Lichten, for example, describes whole schools in which not a single AP student passes an exam. He calls the AP surge in many places a “disaster.” The proportion of students earning the lowest AP score of 1 has doubled over the past 20 years. Of all AP exams taken during high school by the class of 2013 in the District, 51.9 percent received a failing grade of 1. Summarizing the critics’ findings, Harvard University’s Philip Sadler challenges the College Board’s claim that students who fail AP exams still benefit from having taken the course. Such students would be better served by less rigorous courses designed to strengthen their foundations, Sadler says. Yet the surge goes on.

And as a result, by replacing its traditionally minimalist course guidelines with detailed curriculum frameworks, the College Board is now in a position to create a de facto national curriculum.

The massive increase in revenue from government-subsidized testing fees has also allowed the College Board to take over the sort of teacher training once managed by states and districts. Since it writes the exams, signs off on every AP course syllabus, controls teacher training and manages the revision of approved textbooks, the College Board is capable of exercising exceptionally tight control over the curriculum. In effect, the College Board is becoming an unelected national school board, independent of district or state control. Critics have rightly warned that Common Core takes us far down the road to a national curriculum. The College Board, presided over by Common Core architect David Coleman, is swiftly transporting us to the terminus of that highway.

While this summer’s revisions in the AP U.S. History framework eliminate the most biased passages, the broader emphasis remains on themes such as gender and the environment, at the expense of military, diplomatic and political history. Equally important, textbooks and course syllabi were revised with the controversial 2014 framework in mind. They have not been redone in light of the 2015 changes, which would necessitate few additions in any case. So the 2015 revisions are largely cosmetic, designed to mollify critics while forcing minimal changes to the course itself. The College Board can stage-manage this response precisely because it controls every part of the curriculum.

The new AP European History framework reveals the College Board’s intentions more clearly. It is a virtual twin of the 2014 U.S. History curriculum, highlighting colonial oppression and the downside of capitalism, while playing down religion, democratic development and the failings of socialism.

So the debate goes on. But we are having a debate to begin with because, through a combination of runaway expansion and its unprecedented attempt to control course content, the College Board’s AP testing monopoly has broken all bounds. In the absence of competition from a company advised by top traditional scholars, the College Board will have nationalized the curriculum — and pulled it sharply to the left.